Abstract
Abstract. The legal commercialization of cannabis for recreational and medical use has effectively created a new and almost unregulated cultivation industry. In 2018, within the Denver County limits, there were more than 600 registered cannabis cultivation facilities (CCFs) for recreational and medical use, mostly housed in commercial warehouses. Measurements have found concentrations of highly reactive terpenes from the headspace above cannabis plants that, when released in the atmosphere, could impact air quality. Here we developed the first emission inventory for cannabis emissions of terpenes. The range of possible emissions from these facilities was 66–657 t yr−1 of terpenes across the state of Colorado; half of the emissions are from Denver County. Our estimates are based on the best available information and highlight the critical data gaps needed to reduce uncertainties. These realizations of inventories were then used with a regulatory air quality model, developed by the state of Colorado to predict regional ozone impacts. It was found that most of the predicted changes occur in the vicinity of CCFs concentrated in Denver. An increase of 362 t yr−1 in terpene emissions in Denver County resulted in increases of up to 0.34 ppb in hourly ozone concentrations during the morning and 0.67 ppb at night. Model predictions indicate that in Denver County every 1000 t yr−1 increase in terpenes results in 1 ppb increase in daytime hourly ozone concentrations and a maximum daily 8 h average (MDA8) increase of 0.3 ppb. The emission inventories developed here are highly uncertain, but highlight the need for more detailed cannabis and CCF data to fully understand the possible impacts of this new industry on regional air quality.
Highlights
The rapid expansion of one of the United States’ newest industries, the commercial production and sale of recreational cannabis, was recently likened to the millennial “dot-com” boom (Borchardt, 2017)
Where ERi is the total emission rate for cannabis cultivation facilities (CCFs) i based on the sum of emission rates for all j cannabis strains; ECij is the emission capacity for cannabis strain j in facility i, DPWij is the dry plant weight in grams per plant for cannabis strain j, and Plant count (PC) is the plant count number for strain j in facility i
Using realistic bounds on each parameter, we developed seven scenarios, which resulted in estimated emission rates that ranged over an order of magnitude
Summary
The rapid expansion of one of the United States’ newest industries, the commercial production and sale of recreational cannabis, was recently likened to the millennial “dot-com” boom (Borchardt, 2017). With an increasing number of states passing bills to legalize recreational cannabis, the enterprise is set to rival all but the largest of current businesses. The commercial cultivation and sale of cannabis is not subject to the same strict environmental monitoring and reporting procedures as other industries of similar size. While the relaxation of laws has provided certain medicinal and economic opportunities for the states involved, the potentially significant environmental impact on air quality due to the production of cannabis has largely been ignored. Previous research on the wider impacts of cannabis production has been limited due to its federal status as an illegal or controlled substance
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